The goal of this project is to chemically synthesize specific and potent inhibitors of tyrosine-directed protein kinases in vitro. We have chosen the transformation protein of Rous sarcoma virus, pp60[unreadable]src[unreadable], as our model tyrosine-directed protein kinase. The design of the inhibitor will be peptide or peptide-like and is based on the primary sequence of the active site of pp60[unreadable]src[unreadable]. Our long-range goal will be to synthesize specific, in vivo active inhibitors of tyrosine-directed protein kinase. Such inhibitors are expected to aid studies on the biochemical consequences of the tyrosine-specific phosphorylation as a cellular regulation in tumor transformation and growth. It will also provide a prototype drug for the in vivo regulation of tumor growth. To aid our studies on the design of pp60[unreadable]src[unreadable] protein kinase inhibitors and to further our understanding of the mechanism of pp60[unreadable]src[unreadable] as a protein kinase, our short-range goals also include: (1)\the purification of pp60[unreadable]src[unreadable]; (2) the study of the functional domains of pp60[unreadable]src[unreadable], particularly the probable ATP-binding site and the phosphotyrosine active site; (3) the investigation of the phosphotransferring property and chemical reactivity of the high-energy O-phosphate-tyrosine; and (4) enzyme kinetic studies of substrates and inhibitors of pp60[unreadable]src[unreadable]. (B)